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        <span class="token operator">&lt;</span>ul<span class="token operator">&gt;</span>
        <span class="token operator">&lt;</span>li @click<span class="token operator">=</span><span class="token string">&quot;currentView = 'Test'&quot;</span><span class="token operator">&gt;</span>Test<span class="token operator">&lt;</span><span class="token operator">/</span>li<span class="token operator">&gt;</span>
        <span class="token operator">&lt;</span>li @click<span class="token operator">=</span><span class="token string">&quot;currentView = 'Test1'&quot;</span><span class="token operator">&gt;</span>Test1<span class="token operator">&lt;</span><span class="token operator">/</span>li<span class="token operator">&gt;</span>
        <span class="token operator">&lt;</span>li @click<span class="token operator">=</span><span class="token string">&quot;currentView = 'Test2'&quot;</span><span class="token operator">&gt;</span>Test2<span class="token operator">&lt;</span><span class="token operator">/</span>li<span class="token operator">&gt;</span>
    <span class="token operator">&lt;</span><span class="token operator">/</span>ul<span class="token operator">&gt;</span>
    <span class="token operator">&lt;</span>component <span class="token operator">:</span>is<span class="token operator">=</span><span class="token string">&quot;currentView&quot;</span><span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>component<span class="token operator">&gt;</span>
    <span class="token operator">&lt;</span>template<span class="token operator">&gt;</span>
    <span class="token operator">&lt;</span>script<span class="token operator">&gt;</span>
<span class="token keyword">import</span>  Test  <span class="token keyword">from</span> <span class="token string">'./component/testcomponent/testcomponent.vue'</span>
<span class="token keyword">import</span>  Test1 <span class="token keyword">from</span> <span class="token string">'./component/testcomponent/testcomponent1.vue'</span>
<span class="token keyword">import</span>  Test2 <span class="token keyword">from</span> <span class="token string">'./component/testcomponent/testcomponent2.vue'</span>
<span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token punctuation">{</span>
  <span class="token literal-property property">name</span><span class="token operator">:</span> <span class="token string">'app'</span><span class="token punctuation">,</span>
  <span class="token literal-property property">components</span><span class="token operator">:</span><span class="token punctuation">{</span>
    Test<span class="token punctuation">,</span>
    Test1<span class="token punctuation">,</span>
    Test2<span class="token punctuation">,</span>
  <span class="token punctuation">}</span><span class="token punctuation">,</span>
  <span class="token function">data</span> <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span> 
    <span class="token keyword">return</span> <span class="token punctuation">{</span>
      <span class="token literal-property property">currentView</span><span class="token operator">:</span><span class="token string">'Test2'</span>
     <span class="token punctuation">}</span>
 <span class="token punctuation">}</span>
 <span class="token punctuation">}</span>
</code></pre></div><p>通过加载三个组件，在父组件中只显示一个组件，我们通过列表来进行切换
<img src="https://p3-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/c8adcfc7f1ca41f7a7f6979f2c0264c0~tplv-k3u1fbpfcp-watermark.image?" alt="image.png"></p> <p>三个组件分别以简单的一个模板进行测试，并且在created钩子进行输出测试</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token operator">&lt;</span>template<span class="token operator">&gt;</span>
    <span class="token operator">&lt;</span>div<span class="token operator">&gt;</span>
      组件二
    <span class="token operator">&lt;</span><span class="token operator">/</span>div<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>template<span class="token operator">&gt;</span>
<span class="token operator">&lt;</span>script<span class="token operator">&gt;</span>
<span class="token keyword">export</span> <span class="token keyword">default</span><span class="token punctuation">{</span>
    <span class="token function">created</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
        console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">'222'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token operator">&lt;</span><span class="token operator">/</span>script<span class="token operator">&gt;</span>
</code></pre></div><p>以上方式跑起来，我们可以看到点击列表切换的时候，组件也会跟着切换，并且每个组件都会执行created钩子，所以在切换的时候每个组件都会重新渲染，从而造成性能的一些消耗</p> <h3 id="_2-keep-alive"><a href="#_2-keep-alive" class="header-anchor">#</a> 2.keep-alive</h3> <p>通过keepalive我们可以将组件进行缓存，在动态切换组件的时候，能做到尽量少消耗一些性能，并且组件的生命钩子会只执行一次，并不会重复执行
老版本的vue中是这么写keepalive的</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token operator">&lt;</span>component <span class="token operator">:</span>is<span class="token operator">=</span><span class="token string">&quot;currentView&quot;</span> keep<span class="token operator">-</span>alive<span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>component<span class="token operator">&gt;</span>
</code></pre></div><p>2.0中使用属性作为标签的形式</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token operator">&lt;</span>keep<span class="token operator">-</span>alive<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span>component v<span class="token operator">-</span>bind<span class="token operator">:</span>is<span class="token operator">=</span><span class="token string">&quot;view&quot;</span><span class="token operator">&gt;</span><span class="token operator">&lt;</span><span class="token operator">/</span>component<span class="token operator">&gt;</span>

<span class="token operator">&lt;</span><span class="token operator">/</span>keep<span class="token operator">-</span>alive<span class="token operator">&gt;</span>
</code></pre></div><p>通过这样的格式能对多个组件进行优化，每次点击组件的时候，组件进行渲染，只会在第一次触发created钩子函数，相当于加载过的组件都会被缓存下来，当并不是每个组件页面都能用到缓存，如果是需要进行接口请求获取数据，就不适合用keepalive缓存，keepalive主要是用来避免一些不必要的重复渲染</p> <h3 id="_3-activate-钩子函数"><a href="#_3-activate-钩子函数" class="header-anchor">#</a> 3.activate 钩子函数</h3> <p>如果我们将keepalive用于菜单栏，菜单栏有的页面需要接口数据，有的页面不需要接口数据，那么我们不可能将页面分开来，而是如果出现需要调用接口的组件用到了缓存属性，就可以使用activate函数进行判断获取数据，</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token function-variable function">activated</span> <span class="token operator">:</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token punctuation">}</span>
 
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